Polyester film is inherently more chemically stable than either nitrate or acetate and is the best choice for archival use. To date there have been no cases of chemical deterioration of polyester base in archival collections.
While nitrate and acetate can be torn, polyester cannot (except with great effort). It is difficult to splice on traditional splicing equipment so the acceptance of polyester base in cinema films has been slow.
Today, most sheet films (except color) and most microfilm are on polyester base.